Best Zeolite for SCR

Three zeolites dominate commercial SCR for NOx reduction, each optimised for a different operating regime. Cu-SSZ-13 is the default choice for on-road diesel — it provides the best low-temperature activity and the hydrothermal stability to survive DPF regeneration. Fe-SSZ-13 is preferred when sulfur tolerance or high-temperature operation matters more than peak low-temperature conversion. Beta zeolite is a lower-cost option for stationary SCR where extreme thermal cycling does not occur.

Quick Decision Guide

How to Choose

For mobile diesel SCR, start with Cu-SSZ-13. No other zeolite matches its combination of low-temperature activity and hydrothermal durability. The choice of SAR (12 vs 18) trades off fresh activity against long-term durability — SAR 12 for light-duty where peak activity matters most, SAR 18 for heavy-duty where full-useful-life durability is the priority.

If your exhaust contains significant SO₂, evaluate Fe-SSZ-13. Copper-exchanged zeolites are sensitive to sulfur poisoning. At SO₂ concentrations above 10-20 ppm, Fe-SSZ-13 maintains a higher fraction of its initial activity. This is the typical case for marine diesels burning residual fuel and for stationary engines in regions without ultra-low-sulfur fuel.

For stationary SCR without DPF regeneration, Beta is cost-effective. Beta zeolite cannot survive the 800 °C excursions of mobile DPF regeneration, but for stationary applications with stable exhaust temperature below 500 °C, Cu-Beta or Fe-Beta provides adequate performance at lower cost.

For detailed performance data, see the SCR solution hub and SSZ-13 for SCR. When requesting a sample, specify your application, exhaust temperature range, fuel sulfur content, and emission standard.